Known grinders are capable of performing processing, such as grinding, polishing, cutting, or the like, on a workpiece. Such a grinder comprises a spindle that is rotationally driven by a drive device. Various tool accessories are detachably mountable on the spindle. A protective cover that covers the tool accessory from above is normally mounted on the grinder as shown, for example, in Japanese Laid-open Patent Publication No. 2013-78823.